Can you tell when people are lying?

While reading Deborah Tannen's interesting book The Argument Culture, I came across this great passage:

Paul Ekman, a psychologist at the University of California, San Francisco, studies lying. He set up experiments in which individuals were videotaped talking about their emotions, actions, or beliefs--some truthfully, some not. He has shown these videotapes to thousands of people, asking them to identify the liars and also to say how sure they were about their judgments. His findings are chilling: Most people performed not much better than chance, and those who did the worst had just as much confidence in their judgments as the few who were really able to detect lies.

[My emphasis. No citation give in Tannen, and I'm too busy to look it up, so tracking down Ekman's research is left as an exercise for the reader.]